The potassium and sodium conductance systems of frog node of Ranvier are to be characterized using the voltage clamp technique with standard procedures, by the use of fluctuation analysis, and through the study of gating currents. The properties of these channels will be predicted by theories that are generalizations of the Magleby-Stevens theory for gating of acetylcholine sensitive channels from neuromuscular junction. Constants for these quantitative theories will be obtained from potassium and sodium conductance transients produced by step changes in membrane potential. The constants thus obtained will be used to make predictions about the conductance fluctuation spectra and about properties of gating currents. These predictions will be tested compared with experimental results. This procedure will define molecular mechanisms which can and cannot serve as the basis for nerve excitation.